1. Field of the Invention
The present invention is generally directed to setting the spacing between two elements that are moveable with respect to one another. This spacing is commonly referred to as the xe2x80x9cclearancexe2x80x9d between the elements. Some amount of clearance, i.e., within a desired range, is included to minimize friction between the elements. However, manufacturing tolerances and conventional assembly techniques can result in deviations outside the desired range of clearance.
In particular, the present invention is directed to power cutting tools wherein it is necessary to set the clearance between one or more moving, e.g., reciprocating, blades and a blade support member. The term xe2x80x9cpower cutting toolxe2x80x9d includes hand-held power tools such as a hedge trimmers, as well as mechanisms which are not hand-held but whose operation is controlled by the hands of a user, e.g., a lawn mower.
2. Description of the Related Art
In order to perform a desired task using a cutting tool, it is important that the relatively moving blade or blades be separated from each other or from a relatively stationary blade by an optimum clearance for accomplishing the task efficiently.
Conventionally, blade clearance for cutting tools is preset by the manufacturer. Alternatively, it is known to use a spring mechanism to force relative contact between the blades. It is also known to use jam nuts to periodically adjust the clearance. However, many non-professional users do not know how or take the time to make the necessary adjustments.
Examples of known cutting devices associated with reciprocating blades include U.S. Pat. No. 5,771,583 to Kremsler et al., U.S. Pat. No. 5,689,887 to Heywood et al., U.S. Pat. No. 5,075,972 to Huang, U.S. Pat. Nos. 4,879,303 and 4,868,988 to Han, U.S. Pat. No. 4,075,760 to Germain, U.S. Pat. No. 3,579,827 to Grahn, U.S. Pat. No. 3,200,493 to Dodegge, and U.S. Pat. No. 2,275,180 to Holsclaw.
An object of the present invention is to set, within a desired range, the clearance between first and second elements that are constrained to a prescribed relative motion. Thus, it is a further object of the present invention to constrain the first and second elements to the prescribed relative motion while maintaining friction in a desired range. It is yet a further object of the present invention to set an optimal range for the clearance between the first and second elements.
An advantage of the present invention is that the need for grinding blades to give tighter control of their thickness is eliminated.
The above objects and advantages, as well as other objects and advantages that will become clear from the following description of the present invention, are realized by a system for setting a clearance between relatively movable elements. The system comprises a first element; a second element relatively movable with respect to the first element; and a third element penetrating the second element along an axis, the third element being fixed against axial displacement with respect to the first element. The third element having a first axial portion extending a first dimension along the axis between first and second axial ends, the first dimension exceeding a thickness of the second element along the axis, and a second axial portion being connected to the first axial portion at the second axial end and having an enlarged radial dimension relative to the first portion, the second element being interposed between the first element and the second portion. Whereby the first axial end extends into a depression in the first element a second dimension that is less than the difference between the first dimension and the thickness.
The above objects and advantages, as well as other objects and advantages that will become clear from the following description of the present invention, are also realized by a system for setting blade clearance in a power cutting tool. The system comprises a blade support member; a first cutting blade relatively movable with respect to the blade support member; a second cutting blade relatively moveable with respect to the blade support member and with respect to the first cutting blade; and a spacer penetrating the first and second cutting blades along an axis, the spacer being fixed against axial displacement with respect to the blade support member. The spacer having a first axial portion extending a first dimension along the axis between first and second axial ends, the first dimension exceeding a combined thickness of the first and second cutting blades along the axis, and a second axial portion being connected to the first axial portion at the second axial end and having an enlarged radial dimension relative to the first portion, the first and second cutting blades being interposed between the blade support member and the second portion. Whereby the first axial end extends into a depression in the blade support member a second dimension that is less than the difference between the first dimension and the combined thickness.
The above objects and advantages, as well as other objects and advantages that will become clear from the following description of the present invention, are also realized by an apparatus for setting a clearance between relatively movable elements connected by a spacer having a flange. The apparatus comprises a first jaw adapted for engaging a first one of the relatively movable elements; a second jaw including a surface adapted for engaging a second one of the relatively movable elements, the surface having a recess adapted for engaging the flange; and a press moving the first and second jaws toward one another. Wherein the second jaw is adapted for displacing the spacer to deform the first one of the relatively moveable elements, and the surface is adapted for stopping spacer displacement by engaging the second one of the relatively movable elements.
The above objects and advantages, as well as other objects and advantages that will become clear from the following description of the present invention, are also realized by a method of setting a clearance between relatively movable elements. The method comprises orienting adjacent first and second relatively movable elements against a first press jaw; inserting a third element along an axis extending through an aperture in the second element, the third element including a first axial portion extending a first dimension along the axis between first and second axial ends, the first dimension exceeding a thickness of the second element along the axis, and a second axial portion being connected to the first axial portion at the second axial end and having an enlarged radial dimension relative to the first portion, the second element being interposed between the first element and the second portion; aligning a second press jaw against the third element and in opposition to the first press jaw; pressing the third element along the axis against the first element; deforming the first element with the first axial end so as to create a depression extending into the first element a second dimension; whereby axial clearance between the first element, the second element, and the second portion is equal to the first dimension less a combined total of the thickness and the second dimension.
These and other objects and advantages of the present invention are set forth in the description that follows, and in part will be readily apparent to those skilled in the art from the description and drawings, or can be learned by practice of the invention. These objects and advantages of the invention can be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.